The present application is related generally to a turn plate assembly providing rotational movement of a supporting surface upon which a vehicle wheel is disposed when a vehicle is parked during a vehicle inspection or service procedure, and in particular, to a low profile and compact turn plate assembly providing a detachable upper surface or mat configured for translational movement relative to an intermediate surface which in turn provides for rotational movement relative to a stationary underlying lower support layer.
Typically, movable surfaces commonly referred to as turn plates are placed on a vehicle support system surface onto which a vehicle undergoing an alignment measurement or adjustment procedure is driven, such as a lift runway or floor surface. The turn plate is commonly a round plate mounted on a bearing surface, separated from, but flush with the surface of the vehicle support system. The turn plate permits the steered wheels of a stationary vehicle to be steered from side to side without requiring lifting of the vehicle, and simultaneously permits limited translational motion within a horizontal plane. These movable surfaces are utilized in order to prevent the vehicle suspension from binding during steering movement of the vehicle as may be required by an alignment adjustment, inspection, or measurement process.
When inspecting, measuring, or adjusting the alignment of heavy duty vehicles, such as multi-axle trucks, often times a vehicle lift or runway is not utilized, and the procedures are done with the vehicle parked on a solid floor surface. For these types of vehicles, turn plate components are either permanently installed in the floor surface or are temporarily placed in-line with the vehicle wheels, such that the vehicle can be driven up onto the turn plates as needed.
During a conventional vehicle wheel alignment procedure, the vehicle is driven onto the turn plates with the movable surfaces in a locked configuration. Next, sensors are mounted to the vehicle wheels, and the sensors compensated before actual vehicle alignment measurements are acquired. The compensation procedures can be performed by rotating the vehicle wheels with the vehicle raised off the runway surface, or alternatively, by rolling the vehicle over a limited range on the runway surface with the wheel alignment sensors attached to the wheels, i.e. “rolling compensation”. To carry out the procedure for rolling compensation, it is required that the vehicle be rolled a short distance onto the turn plates, such as shown in U.S. Pat. No. 6,209,209 B1 to Linson et al., which is herein incorporated by reference. Often, temporary devices are used to “bridge” the gaps which are present between the floor surfaces and the edges of each turn plate, permitting the vehicle to roll easier and have some support if the roll procedures carry the vehicle off either the front or rear edges of the turn plate. Following the compensation procedure, the bridges, if present, are removed to avoid interfering with the range of motion of the turn plates. The alignment measurements and any corrective procedures are then carried out in a conventional manner during which the movable surfaces may be locked into a stationary configuration from time to time as required, such as shown in U.S. Pat. No. 7,308,971 to Liebetreu et al., which is herein incorporated by reference.
During the rolling compensation procedures, measurements are acquired which are sensitive to movement of the vehicle suspension. In particular, it has been found that the rolling of the vehicle wheel assembly over a gap between the supporting surfaces and the edge of the turn plates can induce undesired reactions in the vehicle suspension system, and correspondingly, reduce the accuracy of measurements acquired during the rolling compensation procedures. Similar effects have been noted due to physical deflection of the turn plate surfaces away from a horizontal alignment due to an uneven distribution of weight from the vehicle as the vehicle wheels roll towards the respective forward and rear edges of the turn plates.
Accordingly, it would be advantageous to provide turn plate in a configuration which maintains a precision planar surface to within a measurement tolerance as a vehicle is driven across, which reduces undesired reaction in the vehicle suspension system induced due to the presence of voids, gaps, or spaces in the vehicle's travel path, which allows for both translational and rotational movement of a vehicle wheel, and which is sufficiently light weight for portable movement between temporary use locations on floor surfaces.